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name: migration-scope-partitioner description: Divides migration work into safe, incremental phases to minimize risk. Use during migration planning. triggers: [migration-planning, large-refactor] outputs: [migration-phases, phase-gates] depends_on: [legacy-behavior-snapshot, system-context-extractor]

Migration Scope Partitioner

Purpose

Breaks large migration efforts into safe, incremental phases that can be delivered and validated independently. Prevents big-bang migrations and ensures continuous delivery of value.

When to Use

• Planning a system migration
• Large-scale refactoring
• Technology stack replacement

Partitioning Steps

1. Assess Migration Scope: Gather behavior snapshots and dependency graphs.
2. Identify Natural Boundaries: Look for domain, data, API, or user journey boundaries.
3. Define Phases: Ensure each phase is independent, valuable, testable, and reversible.
4. Establish Phase Gates: Define GO/NO-GO criteria between phases.

Decision Tree

Copyflowchart TD
    A[Analyze Project] --> B{Tight Coupling?}
    B -->|Yes| C[Use 'Branch by Abstraction']
    B -->|No| D{External Traffic?}
    D -->|Yes| E[Use 'Strangler Fig' Strategy]
    D -->|No| F[Use 'Incremental Cutover']
    C --> G[Define Phase Boundaries]
    E --> G
    F --> G
    G --> H[Create Phase-Gate Checklist]

Review Checklist

1. Independence: Can Phase 1 be deployed and rolled back without Phase 2?
2. Value: Does Phase 1 provide immediate feedback or utility?
3. Risk: Is the blast radius of a phase failure minimized?
4. Timeframe: Is each phase small enough to complete within 2 weeks?

How to provide feedback

• Be specific: "Phase 2 includes both User Profiles and Payment logic, which are tightly coupled."
• Explain why: "Including too much in a single phase increases the risk of a combined failure."
• Suggest alternatives: "Recommend splitting Phase 2 into Phase 2a (Profiles) and Phase 2b (Payments)."

Small steps, continuous validation, always reversible.